Field of the Invention
The present invention relates to catalysts for an olefin metathesis reaction used when olefins are produced by a metathesis reaction wherein a composite metal oxide with plural Group 1 and Group 2 elements are contained as a co-catalyst to thereby improve in the reactivity, and methods for producing the catalyst as well as use thereof.
Description of the Related Art
Metathesis reactions of olefins are reactions whereby the same or different kind of the olefins are converted into new olefins. There are self-metathesis reactions in which, for example, two molecules of propylene are converted into ethylene and 2-butene and cross metathesis reactions in which 2-butene and 3-hexene are converted into two molecules of 2-pentenes.
When the olefin make contact with a metathesis catalyst, the reaction takes place according to a particular structural rule. This is affected by properties of raw materials supplied. This reaction is considered to take place on four central active sites in accordance with chemical equilibrium. The double bond part of olefin faces to the active site to be adsorbed and the hydrocarbon group present at one end of the double bond is exchanged, thereby proceeding the reaction. For example, in cases where of one molecule of 2-butene and ethylene is each brought into reaction, two molecules of propylene can be obtained via an exchange reaction of the hydrocarbon group. Accordingly, if that is applied to any olefin hydrocarbons, various reactions can be predicted.
Propylene is used as a raw material for a variety of industrial products and is primarily obtained from a steam reforming reaction of naphtha with various hydrocarbons, including ethylene, being generated as byproducts. Besides, propylene can be obtained via a propane dehydrogenation reaction and Fischer-Tropsch reaction; but the amount of propylene obtained is smaller than the amount obtained by the steam reforming reaction. Recently, the production of propylene by the above method cannot keep up with the demand for propylene and the production via a metathesis reaction between ethylene and 2-butene has been carried out as well.
In 1964, Phillips Corporation developed a metathesis reaction process of producing ethylene and 2-butene from propylene with a molybdenum oxide catalyst. Subsequently, what was described in Patent Document 1 or Japanese Laid Open Patent Publication No. 2008-519033 was a method employing a catalyst in which tungsten oxide was supported to silica and magnesium oxide as a co-catalyst was developed and completed as a process for propylene production by Lummus Corporation. However, the above document did not employ any composite for the co-catalyst and only showed improved propylene selectivity. There is no mention of the catalytic reactivity. Further, the metathesis catalyst disclosed by the document has a domain of promoting isomerization and thus, when a high concentration of 2-butene is used, causes 2-butene's isomerization to 1-butene. Therefore, 1-butene reacts with 2-butene or the like, thereby generating byproducts to lower the selectivity. Further, the document describes that mixing of isomerization catalysts including magnesium oxide or the like inhibits the metathesis reaction.
Non-Patent Document 1 (Journal of Molecular Catalyst (1985, Vol. 28, Pages 117-131) reports that a tungsten oxide catalyst and magnesium oxide catalyst are mixed to be subjected to a reaction, resulting in improved activity. However, also in the above document, there is no mention of composite co-catalysts for the magnesium oxide catalyst; and the catalytic reactivity is still insufficiently described.
Patent Document 2 (Japanese Patent Publication No. 06-20556) discloses that the activity is improved by using an isomerization catalyst in which magnesium oxide and sodium are supported to γ-alumina having a large surface area and a metathesis catalyst. However, alumina includes acid points and there is a risk that these acid points cause side reactions such as generation of oligomers or the like. Further, because a catalyst with a high activity of isomerization reaction of butene is used in the metathesis reaction, when a high concentration of 2-butene is employed, 2-butene is isomerized to 1-butene and therefore 1-butene reacts with 2-butene or the like in a condition of a high conversion ratio, thereby generating byproducts to lower the selectivity.
Further, Patent Document 3 (International Laid Open Patent Publication No. WO2006/093058 Pamphlet) discloses a method of bringing a catalyst with supported Groups 1, 2, 3, or 12 metals into reaction together with a metathesis catalyst. However, the above document reports that a reaction rate is increased by having a hydrogen gas coexist and the production cost of propylene becomes high because the hydrogen gas must be used. In addition, because hydrogen is used in the reaction, propylene is hydrogenated to propane, thereby lowering the yield of propylene. Also, hydrogenation of raw materials including the hydrogenation of ethylene to ethane takes place, resulting in loss of the raw material. Further, when alumina is used as a carrier, there is a risk, similarly to the above document 2, that the acid point included in the alumina cause side reactions such as oligomers. Also still unknown is a metathesis reaction wherein a co-catalyst is made into a composite to be used.
Patent Document 4 (International Laid Open Patent Publication No. WO2010/024319 Pamphlet) discloses a method of bringing yttrium oxide or a hydrotalcite calcined product into reaction together with a metathesis catalyst. However, yttrium oxide is an expensive rare earth metal and thus there is a problem in terms of cost when yttrium oxide is used industrially. In addition, the hydrotalcite calcined product has a property of being reverted back to hydrotalcite by water; and thus problems arise in storage and practical handlings such as input to a reactor. Further, while there is disclosure with regard to the activity, no disclosure was presented on the selectivity.